I think that history will show (and probably already can show) that what David Petraeus did was turn the tide of the war in Afghanistan. His methods of dealing with the insurgency have left Afghanistan to be a relatively stable and peaceful country, and for that it was worth it.
It depends on the country you are looking at. Petraeus had a great impact in turning the Iraq War around by enlisting local help. Unfortunately, the same cannot be said for Afghanistan, which is still a mess. Now, even with Petraeus long gone and retired, that country is still quite a mess.
General David Petraeus's counterinsurgency has not been worth it. He put more Americans in harms way than was needed or wanted by most of the country. He also encouraged the government to hike up military spending to outrageous levels, which is one of the biggest reasons why the government is in debt right now.
General David Petraeus' counterinsurgency strategy was not worth it because the ultimate end result was far less important than the lives lost and money spent during the war. Many people say that he was just doing his job but the best leaders protect their own and do what is best for their country.